Single unit delayed coking and calcining process



July 2, 1968 3,391,076

SINGLE UNIT DELAYED comm AND CALCINING PROCESS V. D. ALLRED Filed April21, 1966 T0 ST$CK TO 4DISTILLATION y RECYCLE AIR COKABLE HYDROCARBONSCOKING FURNACE INVENTOR.

BY VICTOR D. ALLED United States Patent 3,391,076 SHNGLE lUNiT DELAYEDtCtllKiNG AND CALClNllNG PRUCEESS Victor Dean Alired, Littieton, Cola,assignor to Marathon Oil Company, Findlay, Ohio, a corporation of OhioFiled Apr. 21, 1966, Ser. No. 544,189 tltairns. (Cl. Mid-131) AllidTRACTUh THE DISCLOSURE The present invention comprises a process for thecoking of petroleum hydrocarbons and the calcination of the resultingcoke in situ in a single piece of apparatus comprising in combinationthe steps of conventionally delayedcoking cokable petroleum hydrocarbonsin a delayedcoking drum, so designed as to be capable of withstandingthe temperatures necessary to the calcining of the resulting delayedcoke, and thereafter while said delayed coke remains in the drum inwhich it was coked, igniting said coke and introducing an oxygencontaining gas into said coke at a point removed from the point at whichsaid coke was ignited so as to cause the ignition of volatiles Withinthe coke in a relatively limited combustion zone, venting from the cokedrum any combustion gases formed in said combustion zone, said ventingoccurring at a point on the opposite side of said combustion zone fromthe point of introduction of said oxygen containing gas, controlling theflow of said oxygen containing gas so as to cause coke contacting saidcombustion zone to be calcined to a predetermined desirable degree wtihminimal combustion of the fixed carbon present in said coke wherein thecombustion zone is caused to pass through substantially the entirelength of the coke drum so as to calcine substantially all of the cokescontained therein, and wherein the calcined coke is thereafter removedfrom the coke drum, and related apparatus. Calcined coke is used for avariety of purposes including the manufacture of electrodes forbatteries, aluminum reduction, etc.

The present invention relates to new processes and apparatus for thecombined coking and calcining of petroleum hydrocarbons in a singlepiece of apparatus.

The delayed coking process for the formation of coke from hydrocarbonsis long established and well known. Briefly, the process consists ofheating such hydrocarbons to temperatures sufiicient to cause them tocoke and immediately and rapidly running the hot hydrocarbons into arelatively quiescent chamber generally known as a coking drum. Cokingoccurs in this drum with the noncokable volatilized hydrocarbons beingevolved, generally from the top of the drum, and conveyed to otherrefining processes. After the coking is complete, the coke drum isusually unloaded by removing large manhole covers or doors from the topand bottom of the drum which is in most cases a vertical cylinder withconical or rounded ends. The delayed petroleum coke is a hard densematerial which is removed from the drum only with difficulty. Probablythe most common method of removal of the coke is the use of highpressure e.g., 800 to about 2000 p.s.i.g. water drills which cut outchunks of the coke and permit them to fall through the lower outlet ofthe drum. This process is continued until the drum is empty after whichit is again refilled with hot cokable hydrocarbons.

The disadvantages of these processes include the difficulty inmaneuvering the high pressure water drills in the relatively confinedspace of the coke drum, the time hfldlfl'lb Patented July 2, 1968required to cut out chunks of relatively hard dense coke, and the needfor handling the green or uncalcined coke and transporting it to acalciner.

Every one of these difiiculties is substantially overcome by the newprocess of the present invention and in addition, the need for aseparate calciner is eliminated with a resulting saving in capitalinvestment. The present process permits the in situ calcining of delayedcoke in the same apparatus in which the coking occurs. In addition tosaving capital investment and eliminating transporting of the greendelayed coke, the present invention permits rapid removal of thecalcined coke from the coke drum frequently without the need for anysignificant mechanical fragmentation of the coke. The inventionparticularly utilizes the fact that in most instances a major shrinkagee.g., in the range of 20%, occurs in coke during the calcining process.This shrinkage draws the calcined coke away from the walls of the cokedrum, and causes some fracturing of the coke. In many instances merelyremoving the lower manhole will cause most of the coke to flow from thecoke drum. Any bridging which occurs at the lower manhole can be avoidedby providing a larger aperture or by conventionally rodding or otherwiseagitating the calcined coke.

A basic aspect of the practice of the processes of the present inventionis that the coke is calcined while it is still in the coke drum byigniting the coke preferably at a point near one end of the coke drumand directing an oxygen containing gas e.g., air through the body ofcoke so that the gas reaches the point of ignition, forming therelatively limited combustion zone and then passes out from theapparatus at a point on the other side of the combustion zone from thepoint of ignition.

Thus one principle of the present invention involves theoxygen-containing gas contacting the coke at a point where the coke isrelatively cold (well below ignition temperature) because it has not yetpassed through the combustion zone. The oxygen containing gas thenpasses up through this relatively cool coke until it meets thecombustion zone where the volatiles are burned. The combustion gasesfrom the combustion zone then continue on and exit through a point onthe opposite side of the combustion zone from the point of injection ofthe oxygen. Preferably, the quantity of oxygen hydrogen containing gasesinjected is so controlled as to cause combustion gases evolved from thecombustion zone to be oxygen-deficient This prevents any furtheroxidation of coke which has already been calcined. The hot combustiongases will in most instances, serve to remove further volatiles from thecoke which has already passed through the combustion zone.

In short, the process of the present invention provides a process forthe coking of petroleum hydrocarbons and the calcination of theresulting coke in situ in a single piece of apparatus comprising incombination the steps of conventionally delayed-coking cokable petroleumhydrocarbons in a delayed coking drum so designed as to be capable ofwithstanding the temperatures necessary to the calcining of theresulting delayed coke, and thereafter while the delayed coke remains inthe drum in which it was coked, igniting the coke and introducing anoxygen containing gas into said coke at a point removed from the pointat which said coke was ignited so as to cause the ignition of volatileswithin the coke in a relatively limited combustion zone, venting fromthe coke drum any combustion gases formed in the combustion zone, saidventing occurring at a point on the opposite side of said com- 3 bustionzone from the point of introduction of said oxygen-containing gas,controlling the flow of said oxygencontaining gas so as to cause cokecontacting said combustion zone to be calcined to a predetermineddesirable degree with minimal combustion of the fixed carbon present insaid coke.

The drawing is a schematic diagram of typical apparatus for practice ofthe present invention.

Cokable hydrocarbons preferably the petroleum residual from adistillation of crude petroleum, are heated to a coking temperature inthe general range of from 700 to 1200 and most preferably from about 880to about 960 degrees F. in a coking furnace l. The hot hydrocarbons fromthis coking furnace pass through open valve 2 into a coke drum 3 untilthe coke drum is full. The vaporized portions of the hydrocarbons feedto the coke drum, pass out of the drum to the top outlet 10, and go onto a distillation or partial condensation in which they are separatedinto fractions which are recovered. At this time valve 7 is open andvalves 8 and Ill are closed. After the coke drum is about full, valve 2is closed and the coking hydrocarbons are allowed to remain quiescent.The coking takes from six to about thirty hours, more preferably from 12to about 20 hours, during which time they cool substantially andsolidify, forming delayed coke 4.

With valves 7 and 2 closed and valves 8 and 11 open, air is now forcedby means of blower 9 into the coke drum for moving upward through thebed of coke. The coke bed is ignited near the top by use of an igniter 6which may be a railroad flare, or a gas or electric powered ignitiondevice.

The upward moving air meets the coke at the point of ignition then formsa relatively shallow combustion zone extending across the crosssectional area of the coke drum. Preferably, this combustion zone willbe of a depth of from about A to about 4 feet and more preferably, fromabout /2 to about 2 feet as measured along the major axis of the cokedrum.

Now valve 11 is operated to control the rate of air flow into the cokedrum so that virtually all of the oxygen is consumed in the combustionzone and the area above the combustion zone is deficient in oxygen. Thiscontrol is very much preferred in order to prevent unnecessarycombustion of fixed carbon values from the coke after it has beencalcined by contact with the combustion zone. The temperature in thecombustion zone is maintained at above 1000 degrees F. and in mostcases, lower than 2800 degrees F. While the temperature will varysomewhat according to whether full or partial calcination is desired andaccording to the percent volatile content of the coke prior tocalcination (the green coke), the preferred temperature range in thecombustion zone will generally be from about 1400 to about 2400 degreesF. Additional control of the temperature in the combustion zone and ofthe flow of oxygen into the coker can be achieved by recycling some ofthe exhaust gases which exit through upper outlet of the coke drum andthrough valve 8. By throttling valve 14 and opening valve 13 recycle ofthese exhaust gases can be controlled to decrease the oxygen content ofthe gases entering the coke drum through the bottom outlet 12.

In most cases it will be desirable that the combustion zone movedownward at a rate of about /2 to about 6 feet/hour, and more preferablyfrom about 1 to about 3 feet per hour. Various modifications, includingthe presence of two combustion zones e.g., by igniting the mass of cokein the coke drum at both the top and bottom surfaces and thenintroducing oxygen into the mid-point of the drum, can be employed.

Automatic control systems for the measurement of temperature within thecoke drum and corresponding control of the oxygen content and thequantity of the oxygen-containing gases can be employed where desirable.

The materials of Construction of the coke drum 3 must be suflicientlytemperature resistant to permit the attaining of the desiredtemperatures in the combustion zone. In most instances, a relativelyconventional steel coke drum which has been specially lined withsuflicient thickness of refractory materials e.g., castable refractoriesor firebrick masonry, will be utilized.

The products of the process of the present invention are of course,suitable for a wide variety of uses including use as fuels and asmetallurgical additives.

After the combustion zone has traveled down the entire length of thecoke drum as shown in the drawing, the drum will, in most instances, befilled with a mass of shattered coke and relatively large pieces. Thismass of coke will, because of shrinkage due to devolatilization, havepulled away from the walls of the coke drum and be loose. Also, becausethe calcined coke is relatively friable, the larger chunks may bequickly and readily broken by rodding or similar agitation conductedeither by a rod manipulated from the upper manhole 10, or by rod orother breaking device extending upward from the lower manhole 12.

It will be understood that the above described embodiment is merelyillustrative and is not to be considered as limitative of the scope ofthe invention. The invention is subject to a wide variety of variationsand modifications which will be apparent to persons skilled in the art,all of which are to be taken as being included within the claimsappended hereto.

What is claimed is:

1. A process for the coking of petroleum hydrocarbons and thecalcination of the resulting coke in situ in a single piece of apparatuscomprising in combination the steps of conventionally delayed cokingcokable petroleum hydrocarbons in a delayed coking drum which issubstantially a vertical cylinder so designed as to be capable ofwithstanding the temperatures necessary to the calcining of theresulting delayed coke, and thereafter while said delayed coke remainsin the drum in which it was coked, igniting said coke and introducing anoxygen containing gas into said coke at a point removed from the pointat which said coke was ignited so as to cause the ignition of volatileswithin the coke in a relatively limited combustion zone, venting fromthe coke drum any combustion gases formed in said combustion zone, saidventing occurring at a point on the opposite side of said combustionzone from the point of introduction of said oxygen containing gas,controlling the fiow of said oxygen containing gas so as to cause cokecontacting said combustion zone to be calcined to a predetermineddesirable degree with minimal combustion of the fixed carbon present insaid coke wherein the combustion zone is caused to pass throughsubstantially the entire length of the coke drum so as to calcinesubstantially all of the cokes contained therein, and wherein thecalcined coke is thereafter removed from the coke drum.

2. The process of claim 1 wherein the coke is ignited substantially athe top of the coke drum.

3. The process of claim 2 wherein the calcined coke is removed throuhg aclosable aperture located near the bottom of the coke drum.

4. Apparatus for the coking and in situ calcining of cokable petroleumhydrocarbons comprising in combination a furnace for heating saidhydrocarbons to at least their coking temperature, a coke drum having aninlet for said hydrocarbons connected to the outlet of said furnace,having an exhaust outlet for removing noncokable hydrocarbon vapors,having ignition means, having at least one inlet for the injection ofoxygen containing gases, having an outlet for the venting of combustionproducts, and having at least one closable aperture located in itsbottom portion for full removal of calcined petroleum coke, saidapparatus being so constructed as to be capable of withstandingtemperatures at least as high as those required to calcine the petroleumcoke to a pre-determined desired degree.

5 5. The apparatus of claim 4 wherein the coke drum 3,116,231 comprisesa steel outer jacket lined with a refractory 3 130 14 material.

References Cited 3173852 3,249,528 UNITED STATES PATENTS 5 2,732,332l/1956 Geller 208-92 2,813,823 11/1957 Putnam 201-37 Adee 208-46 Plaster208--106 Smith 20846 Allred 20846 HERBERT LEVINE, Primary Examiner.

